36 BULLETIN OF THE BUREAU OF FISHERIES. 



C. Dorsal branchial arch muscles. 



7. Levatores arcuum branchialium. 



8. Interarcualisdorsalisobliquus, posterior. 



9. Interarcualisdorsalisobliquus, anterior. 



10. Adductor arcuum branchialium, anterior. 



11. Adductor arcuum branchialium, posterior. 



12. Transversi dorsalis, anterior. 



13. Transversi dorsalis, posterior. 



D. Ventral branchial arch muscles. 



14. Interarcuales ventralesobliqui. 



15. Transversi ventralis, anterior. 



16. Transversi ventralis, posterior. 



17. Pharyngo-clavicularis extemus. 



18. Pharyngo-clavicularis intemus. 



E. Mandibular and hyoid arch muscles. 



(lb. Adductor mandibulae, mandibular portion.) 



19. Intermandibularis. 



20. Geniohyoideus. 



21. Hyohyoideus. 



22. Stemohyoideus. 



SUPERFICIAL DORSAL HEAD MUSCLES. 

 ADDUCTOR MANDIBUL^ (THE MASSETER OF .\GASSIZ, OR RETRACTOR ORIS OF OWEN). 



This is the largest muscle in the head. It forms the fleshy mass just posterior to 

 the eye which for its delicacy of flavor the fishermen prize under the name "salmon 

 cheeks." 



The adductor mandibulae is in two divisions that are almost though not quite dis- 

 tinct and separate. There is a cephalic division above the angle of the jaw, and a 

 mandibular portion lying chiefly below and along the inner border of the dentary. 



The cephalic division of the adductor is in old specimens often more or less indis- 

 tinctly separated into three divisions, as described by Allis" ior Amia. These divisions 

 are, however, not bounded by more than the thinnest of endomysial membranes and are 

 intimately fused toward the tendon of insertion. In fact they are of lesser importance 

 and scarcely justify the dignity of special designation. The cephaUc division will 

 therefore be described as a whole. 



(a) The cephalic division of the adductor mandihulcc has an extensive surface of origin 

 which includes (i) the anterior border of the preopercle for most of its extent, (2) the 

 entire surface of the quadrate, (3) the metapterygoid, and (4) the hyomandibular. 

 Some fibers arise (5) from the connective tissue sheath covering the levator arcus 

 palatini and from the post-orbital septum. The muscle fibers converge in a sweeping 

 curve or general fan-shaped whorl in the dorso-ventral direction to their attachment 

 in the broad tendon at the angle of the jaw. The extreme posterior fibers run anteriorly 

 and somewhat downward toward the ventral margin of attachment. This division of 

 the muscle is attached by a short, heavy, rather broad tendon into the outer margin 

 of the posterior part of the articulare. The tendon is intimately fused with the con- 

 nective tissue that binds the articulare with the premaxillary and the quadrate bones. 



o Allis, Edward Phelps, loc. cit. 



